Obstructive sleep apnoea-hypopnoea syndrome (OSAHS) is a common condition affecting approximately 0.3-4 % of the middle-aged population. A hereditary component to the condition has long been identified but the genetic basis has been difficult to elucidate. Not least of the difficulties resides in a single definition of the phenotype. In an attempt to unravel some of the components, which might contribute to the expression of the syndrome, 'intermediate phenotypes' such as craniofacial structure, obesity, and upper airway control have been utilised. A number of gene polymorphisms have been explored in association with these, and two genome-wide scans have identified potential regions that may be of interest in further defining the 'intermediate phenotypes'. This paper focuses largely on human studies with an update on the most recent work in the area. A short discussion on methods of genetic studies is also provided.